Segmented turbine ring for a turbomachine, and turbomachine fitted with such a ring

ABSTRACT

The segmented ring has the gaseous hot flow of the turbomachine passing through it and comprises:
         a plurality of segments assembled by means of sealed connection involving sealing strips, provided in the mutually-facing radial faces of said segments the internal lateral faces of which delimit the flow path along which the hot gaseous flow travels; and   through-orifices, formed in said segments, to carry external fresh air towards their radial and internal faces.       

     Advantageously, one, the lower one, of the sealing strips of the means of connection is designed to lie close to the lateral internal faces of said segments and to run parallel to them, passing through a cooling chamber formed in the radial faces of the segments and into which said orifices open.

BACKGROUND OF THE INVENTION AND DESCRIPTION OF THE PRIOR ART

The present invention relates to a segmented turbine ring for a turbomachine.

In a preferred, although not exclusive, application of the invention, the turbomachine is intended for the aeronautical field and constitutes the turbojet engine or the like of an aircraft such as an airplane.

In general and simplistically speaking, such a turbomachine comprises, in the direction in which the hot gaseous flow travels, a compressor, a combustion chamber and a turbine ending in a gas jet pipe nozzle. The turbine, particularly the high-pressure turbine, usually comprises, downstream of a nozzle guide vanes assembly with fixed vanes positioned on the outlet side of the combustion chamber, a rotor with vanes that rotate under the action of the hot gaseous flow leaving the combustion chamber and passing through the nozzle guide vanes assembly. Arranged around the rotor is the segmented ring that forms the rotor casing delimiting the flow path for the hot gaseous flow passing through the turbine.

Such a segmented ring notably comprises:

a plurality of segments assembled one after the other by means of sealed connection involving sealing strips fitted into opposing slots formed in the mutually-facing radial faces of said adjacent segments the lateral internal faces of which delimit the flow path along which the hot gaseous flow travels; and

through-orifices formed in at least some of said segments to carry fresh air external to said assembled segments towards their internal radial and lateral faces.

Given its proximity to the combustion chamber and the fact that the hot gaseous flow passes through it, the segmented ring is subjected to considerable thermomechanical stresses which means that it needs to be effectively cooled via the orifices to guarantee that it will operate reliably and exhibit good endurance.

Although in service such a segmented ring yields good results, it would however seem that the hot gaseous flow has a tendency, at the internal periphery of the ring, to rush into the spaces or clearances that there are between the radial faces of the segments connected by the sealing-strip connecting means, leading to a scoop effect. This results in recirculations of the hot air flow entering and leaving the clearances between the adjacent segments until it reaches the connecting sealing strips distant from the lateral internal faces of the segments that delimit the flow path.

Because of this repeated recirculation, the effectiveness of the orifices opening into the radial faces and carrying fresh air external to the ring towards the hot zones that are to be cooled (the radial and internal faces of the segments) is lowered and impaired. As a result, the ring cooling is no longer optimal, leading to a reduction in ring life and a need to check or change the ring more frequently, or even leading to a weakening of the ring. What is more, because of this scoop effect, the aerodynamic efficiency of the high-pressure rotor is adversely affected by these recirculations of hot air in the intersegment clearances, disrupting the aerodynamic flow along the ring envelope defined by the lateral internal faces of these segments.

Furthermore, a cooling chamber may be formed in the radial faces of the adjacent segments of the ring, with the air-carrying orifices opening into the chamber. This embodiment does not, however, prevent the scoop effects.

It is an object of the present invention to remedy these disadvantages and the invention therefore relates to a segmented turbine ring the design of which makes it possible to maintain optimum cooling of the segments by avoiding the recirculations of hot air between these segments.

SUMMARY OF THE INVENTION

To this end, the segmented turbine ring, through which a hot gaseous flow can pass and as defined hereinabove, which additionally has at least one cooling chamber formed in the radial faces of the adjacent segments and into which said orifices open, is notable according to the invention in that at least one, the lower one, of the sealing strips of the means of connection that assemble consecutive segments by their radial faces, is designed to lie close to the lateral internal faces of said segments and to run parallel to them, substantially from the upstream transverse face to the downstream transverse face of said assembled segments, passing through said cooling chamber, and in that each lower sealing strip fits into slots made in the radial faces of two adjacent segments parallel to and as close as possible to said lateral internal faces and in the periphery delimiting said chamber.

Thus, by virtue of the invention, by arranging lower sealing strips as close as possible to the lateral internal faces of the segments, the hot air flow is still channeled along the flow path delimited by these lateral internal faces without being able to rush or rise into the intersegment clearances between the radial faces and therefore without detracting from the cooling of the hot zones of the segments by the chambers created between the adjacent segments and which concentrate the fresh air. The scoop effects are therefore practically eliminated with an improvement to the cooling of the relevant hot zones of the ring as the fresh air arriving in the chambers via the orifices is concentrated towards said hot zones that are to be treated, i.e. towards the internal and radial lateral faces of the segments and the intersegment clearances as far as the sealing strips close to said lateral faces. Because of the sealing strips arranged in the slots as close as possible to the lateral internal faces, and in the periphery of the chambers, the hot gaseous flow is thus channeled to best effect and the scoop effect and other leakages out of the ring are avoided.

In one particular embodiment, said cooling chamber is defined by two mutually-facing recesses formed in the radial faces of two assembled segments in order to open into their lateral internal faces. By way of example, the mutually-facing recesses that form the chamber each have a substantially rectangular hollow profile, with a bottom parallel to said lateral internal face of the corresponding segment, two sides parallel to the transverse faces of the segments and in which the slot accommodating the lower sealing strip terminates, and a main face parallel to the radial face of each of them.

Hence, to contribute to eliminating the abovementioned recirculations, the bottom of the recesses is close to the slot accommodating the lower sealing strip with the external fresh air orifices opening into said recesses. With a chamber of a smaller size, of lesser depth, combined with the sealing strips close to the internal faces, recirculations of hot gases are avoided while at the same time suitable cooling of the hot zones is maintained by the fresh air orifices concentrated in the recesses towards these zones.

Advantageously, for even cooling, the cooling chamber formed by the mutually-facing radial faces of two assembled segments lies approximately in the central part thereof, between their upstream and downstream transverse faces.

According to one particular embodiment, in order best to conform to the slots and the chambers, said lower sealing strip that assembles two consecutive segments comprises several parts, a front part between the upstream transverse face and the chamber, a central part that hugs the periphery of said chamber, and a rear part between the chamber and the downstream transverse face.

In this case, the central part of each lower sealing strip may comprise in turn a straight sub-part attached into the bottom of the mutually-facing recesses and two sub-parts at a right angle, one of the branches of each right angle running along the corresponding side of the chamber and the other branch being superposed with the relevant end of the respective front or rear part of the sealing strip.

As an alternative, it is possible to conceive of each lower sealing strip being produced as a one-piece element.

The invention also relates to a turbomachine comprising at least one turbine with a rotor housed in a segmented ring. Advantageously this ring is as defined hereinabove.

DESCRIPTION OF THE DRAWINGS

The figures of the attached drawing will make it easy to understand how the invention may be embodied. In these figures, identical references denote similar elements.

FIG. 1 is a radial view of a turbine ring segment with the associated means of connection involving sealing strips.

FIG. 2 is an exploded perspective depiction of the radial face of the ring segment illustrated in FIG. 1, with the associated cooling chamber and the associated means of connection involving sealing strips.

FIG. 3 is a view in cross section on A-A of FIG. 1 of two ring segments joined by said means of connection.

DESCRIPTION OF THE PREFERRED EMBODIMENT

In the usual way, a gas turbine, such as a turbojet engine in the example described, comprises a high-pressure turbine 1 depicted in part in FIG. 1 and which is situated, in the direction in which the hot gaseous flow F travels, downstream of the combustion chamber and of a fixed nozzle guide vanes assembly that guides the associated gaseous flow (the chamber and the nozzle guide vanes assembly not being illustrated in FIG. 1).

This high-pressure turbine 1 notably comprises a rotor or impeller 2 through the vanes 3 of which the hot gaseous flow F leaving the nozzle guide vanes assembly passes, so that it can turn them.

To channel the hot gaseous flow F passing through the rotor 2 and then moving on towards a low-pressure turbine, the high-pressure turbine 1 comprises a segmented ring 4 which surrounds the rotor, i.e. the periphery of the vanes 3 thereof. To do that, the segmented ring 4 is made up of a plurality of identical segments 5, assembled one after the other by way of means of sealed connection 6 to form the segmented ring.

Each segment 5, like the one depicted in a radial view in FIG. 1, is schematically borne by a cylindrical casing 7 of the turbine which externally surrounds the segmented ring 4, delimiting an annular space 8 between them which can be entered, via holes 9 provided in this casing 7, by fresh air F1 flowing around the central spool of the turbine, i.e. around the combustion chamber, the nozzle guide vanes assembly and the high-pressure and low-pressure turbines. The cylindrical casing 7 and the segmented ring 4 are connected by the usual known flanges and assemblies 10 used for sealing and connecting.

Each segment 5 of the ring 4 structurally has two radial faces 11 (just one of them is visible in the figures) converging towards the longitudinal axis A of the turbine, on which axis the compressors, turbines, disk and other components thereof are aligned and which, in FIG. 1, is exaggeratedly close to the illustrated segment 5. The two radial faces 11 are laterally connected by an internal face 12 facing towards the vanes 3 of the rotor 2 and by an external face 13 facing towards the casing 7, the internal and external lateral faces having a curved profile to form the ring. Further, these four faces, these respectively being the radial faces 11, the internal face 12 and the external face 13, end, in the direction in which the gaseous flow F travels, in an upstream transverse face 14 and a downstream transverse face 15. All of these faces together delimit the structural wall 5A of each segment. As for all of the internal lateral faces 12 of the assembled segments 5, they together delimit the envelope 16 that channels the hot gaseous flow F. FIG. 1 also shows that the free end 17 of the vane 3, depicted in chain line, of the rotor is close, give or take the functional clearance, to the lateral internal face 12 of the segment forming the envelope.

The means of sealed connection 6 connecting two adjacent or consecutive segments 5 by their mutually-facing radial faces 11 are defined by sealing strips or leaves which, as FIGS. 1, 2 and 3 show, fit into respective slots 18, 18A formed in the wall 5A of the segments to emerge perpendicularly in the radial faces 11.

In this exemplary embodiment, the means of connection 6 between two adjacent segments 5 are defined by two sealing strips, an upper sealing strip 19 towards the external lateral face 13 of the segments and housed in the slot 18A, and a lower sealing strip 20 towards the lateral internal face 12 of the segments and housed in the slot 18, said slots for housing the sealing strips running parallel to the internal faces 12. Advantageously, according to the invention, each lower sealing strip provided in the corresponding radial faces of the segments is designed to lie parallel to and as close as possible to the envelope 16 of the assembled segmented ring 4, i.e. near to the lateral internal faces 12 of the segments. The reason for this is to prevent as far as possible hot gases from the flow F from getting in between the radial faces of the segments in which, as will be seen later on, the external fresh air F1 of the space 8 enters to cool the segmented ring 4, notably its zones in contact with the hot gaseous flow. Additional connecting sealing strips could of course be added to the aforementioned two, the important thing being to have a lower sealing strip close to the lateral internal faces of two adjacent segments.

For this purpose, formed in each radial face 11 of the segments is at least one recess or open cavity 21 which, with the recess opposite provided in the radial face of the adjacent segment (FIG. 3), forms a chamber 22 and into which through-orifices 23 open placing the external annular space 8 provided between the ring and the casing in fluidic communication with the chamber 22 and therefore the intersegment space or clearance 24 between the radial faces 11 of the two adjacent segments. In particular, the recesses 21 are identical and each, in the plane of the radial face, is substantially rectangular in shape and located substantially in the middle part of the radial face 11, between the upstream 14 and downstream 15 faces. Any other shape and any other location of the recesses could be conceived of without departing from the invention.

Structurally speaking, each open recess 21 opens into the lateral internal face 12 and is delimited by: two sides 25 that are parallel to each other and to the upstream 14 and downstream 15 faces, in the two sides opening the slot 18; a bottom 26 parallel to the slot 18 (and therefore to the internal lateral face 12) and of course further away from the internal face than the slot; and a set-back main face 27 parallel to the radial face 11. The depth of the recesses between the internal faces 12 and their bottom 26 is small and so determined to avoid recirculated flow F entering the chambers.

It can be seen, particularly with regard to FIGS. 2 and 3, that three cooling orifices 23, obtained by drilling, are provided in the wall 5A of the corresponding radial rims 28 of the segments and place the annular space 8, in which fresh air F1 from the holes 9 is located, in communication with the chambers 22 which are therefore “cooled” opening obliquely into the set-back main face 27 of the recesses 21. The outputs from the three orifices arriving in the recess are here aligned, parallel to the bottom 26. The number and location of the orifices could once again differ provided that the fresh air concentration arriving in the limited-size recesses that form the chambers results in effective treatment of the hot zones concerned.

The lower sealing strip 20 extends over practically the entire width of the ring, defined by the distance separating the upstream 14 and downstream 15 transverse faces of the segments 5, and is housed in the slot 18 which is therefore made in two portions separated by the middle recess 21, from the parallel sides 25 of each recess up to near the corresponding transverse face 14, 15, passing via the elbowed periphery of the middle open recess, i.e. along the two lateral sides and the bottom. Thus, connection is over practically the width of the segments.

The slot 18 that partially houses the lower sealing strip 20 is parallel to the internal face 12 and close to an end chamfer 30 provided at the intersection between the corresponding radial face 11 and the lateral internal face 12. The minimum distance of these lower slots 18 from the lateral internal faces 12 of the segments is of course determined so as not to detract from the integrity of the segmented ring 4 when the turbine is in operation.

For example, each lower sealing strip 20 that connects two adjacent segments 5 is made up, in the embodiment shown in FIG. 2, of several parts, two straight parts 31, these respectively being a front and a rear part, which are attached to the respective portions of the slot 18, and a central part 32 collaborating with the recess 21. This central part 32 is in turn broken down into a straight sub-part 33 parallel to the parts 31 and attached against the bottom 26 of the recess, and into two right-angle sub-parts 34, one of the branches 35 of each right angle running along the corresponding parallel side 25 of the recess and the other branch 36 being superposed with the corresponding end of the straight part 31 and to do so fitting into a space 37 provided in each portion of slot 18.

Dimensionally, as shown by FIG. 3, the depth of the slots 18 combined, formed by the two adjacent segments connected by these means of connection 6, is similar to the width of the lower sealing strip 20 concerned, i.e. of the parts that make it up, a functional clearance or space 24 being left between the segments.

It is also possible to conceive of producing the lower sealing strips 20 as a one-piece element.

As for the upper sealing strip 19, this is of one piece and fits into the two semi-emerging slots 18A provided in the rims 28 of the adjacent segments, and opening into the radial faces 11 as shown by FIGS. 2 and 3.

The segments 5 thus assembled by the means of connection 6 form the ring 4 of the rotor 2 of the high-pressure turbine. The objectives of cooling and lower wear rate of such a ring are achieved by having the lower sealing strips 20 as close as possible to the envelope 16 of the lateral internal faces 12 along the inside of which the gaseous flow F travels, and by the shallow chambers 22 created, with the orifices for fresh air directed towards the hot zones. This arrangement makes it possible to avoid the scoop effects (recirculation of hot gases) in the intersegment spaces while at the same time ensuring optimum cooling of the segments 5 thanks to the chambers 22 of which the concentration of cooling air coming from the associated communicating orifices 23 provides best ventilation for the hot zones of the segments, where the gaseous hot flow is travelling. 

1. A segmented turbine ring, through which the hot gaseous flow of a turbomachine can pass and comprising: a plurality of segments assembled with one another by means of sealed connection involving sealing strips, provided in the mutually-facing radial faces of said segments the internal lateral faces of which delimit the flow path along which the hot gaseous flow travels; through-orifices, formed in said segments, to carry fresh air coming from outside to said assembled segments towards their radial and lateral internal faces; and at least one cooling chamber formed in the radial faces of the adjacent segments and into which said orifices open, wherein at least one, the lower one, of the sealing strips of the means of connection that assemble consecutive segments by their radial faces, is designed to lie close to the lateral internal faces of said segments and to run parallel to them, substantially from the upstream transverse face to the downstream transverse face of said assembled segments, passing through said cooling chamber, and wherein each lower sealing strip fits into slots made in the radial faces of two adjacent segments parallel to and as close as possible to said lateral internal faces and in the periphery delimiting said chamber.
 2. The ring as claimed in claim 1, in which said cooling chamber is defined by two mutually-facing recesses formed in the radial faces of two assembled segments.
 3. The ring as claimed in the preceding claim, in which the mutually-facing recesses that form the cooling chamber each have a substantially rectangular hollow profile, with a bottom parallel to said lateral internal face of the corresponding segment, two sides parallel to the transverse faces of the segments and in which a slot accommodating the lower sealing strip terminates, and a main face set back parallel to the radial face of each of them.
 4. The ring as claimed in claim 3, in which the bottom of the recesses is close to the slot accommodating the lower sealing strip with the external fresh air orifices opening into said recesses.
 5. The ring as claimed in claim 1, in which the cooling chamber formed by the mutually-facing radial faces of two adjacent segments lies approximately in the central part thereof, between their upstream and downstream transverse faces.
 6. The ring as claimed in claim 1, in which said lower sealing strip that assembles two consecutive segments comprises several parts, a front part between the upstream transverse face and the chamber, a central part that hugs the periphery of said chamber, and a rear part between the chamber and the downstream transverse face.
 7. The ring as claimed in claim 6, in which the central part of each lower sealing strip comprises a straight sub-part attached into the bottom of the mutually-facing recesses and two sub-parts at a right angle, one of the branches of each right angle running along the corresponding side of the chamber and the other branch being superposed with the relevant end of the respective front or rear part of the sealing strip.
 8. A turbomachine comprising at least one turbine with a rotor housed in a segmented ring, wherein said segmented ring is as defined in claim
 1. 